Jennifer Aniston is definitely known for having one of the best bods in the biz.

She's got an incredibly fit physique, especially at 43!

What's her secret??

Apparently its a smoothie she drinks all day, one day a week, usually a Saturday.

A source said:

"The drink is made up of fresh, organic vegetables. Beetroot, cucumbers, spinach, garlic, carrots, celery and kale."

A nutritionist said:

"The alkaline vegetables prevent bloating, help ease water retention and even mood swings. Beetroot helps clean the blood of toxins, celery and carrots boost potassium and sodium levels, and kale and parsley offer immense benefits to the brain, so you'll feel less stressed. The drink is filling so should be easy to do for one day a week, but make sure it's part of a healthy balanced diet."

The smoothie not only keeps her happy and healthy, but it's apparently tasty enough to drink for a whole day!

Wanna make her smoothie and drink like Jennifer?

Just grab:

- Six organic cucumbers

- Three large organic beets

- Two bunches spinach

- One bunch organic kale

- Fresh garlic and ginger

- One bunch organic carrots

- A stick of celery

Now you need a juicer (or a high powered blender could work in a pinch, it'd just be much thicker and maybe need to be cut with some water). Then just:

"Pulp all the vegetables together in a juicer. Add a little cayenne pepper or a herb such as parsley, to make the juice blend taste like a vegetable soup.

This isn't the first time the 39-year-old's figure has caused controversy. As we reported in January, the American Pie stunner was accused of using Photoshop to make her already narrow waist even smaller.

Reid has admitted to getting plastic surgery in the past to make changes to her abdominal area and breasts -- but the actress asserts that she naturally has a lean shape.